In the preparation of silage and the like from long-stalk row crops such as corn, it is common practice to provide a field chopper or harvester on a vehicle structure adapted to move along the rows of the crop material. Normally the pickup device has two mouths, each aligned with a respective row and provided with respective chains or other crop-advancing mechanism for drawing the stalks into the machine, holding them while they are severed from the ground, and advancing such crop material to the throat of the machine. In a field chopper the throat of the machine is generally provided with a pair of feed drums or rolls which advance the stalks end-on toward the rotating chopper blades. The chopper blades comminute the stalks and blow the crop into silage wagons or other vehicles for transportation to the silo.
The mower or sickle blades are provided at the junction of each mouth with a respective channel along which a pair of chains entrains the stalks to the throat of the machine as just described. The chains are provided with entraining projections, teeth or noses which may be staggered on opposite sides of the channel to enable the stalks to be gripped between projections of the opposing chains.
The two channels converge toward and terminate at the throat of the machine where the crop material advanced through the channels is united.
Attempts have been made to provide pickup heads of the aforedescribed type, e.g. so-called corn heads, capable of handling more than three rows of crops. Such attempts have been, for the most part, failures because of the problem which arises when the width of the pickup heads at the intake side, i.e. the span across three or more rows, is relatively large while the throat of the machine is comparatively small and narrow.
Thus, when more than three rows are to be swept by the pickup head, problems arise in feeding the crop material of the respective channels together at the throat of the machine.
It has been proposed to obviate the problem by passing one of the stalk feed mechanisms over another so that, at least in the region of the throat, they overlap. In other arrangements, one or another of the mechanisms terminates short of the throat and at a relatively large distance from the feed rollers or drums of the chopper.
Both of these systems have been found to be disadvantageous since the positive advance of the crop material is interrupted close to the throat of the chopper and blockage and packing of the crop material may occur.
Furthermore, when three or more channels are provided, each with respective sets of feed chains running from the respective mouths, problems are encountered because of the considerable lengths of chain which must be driven over the full channel lengths and in relatively large numbers. The chains are costly and frictional drag on them requires that the drive system be made especially powerful. This leads to an increase in size of the driving engine, the power distribution mechanism, gearing and the like.
Furthermore, in almost all of the conventional systems, the chains operate in paired relationship over the full length of the channels, i.e. the full distance between the respective mouths and the throat of the machine, thereby increasing wear and drag and resulting in interference between the projections of the opposite chaines. Such interference may result in damage to the drive system.
It has also been proposed to eliminate the problem by gathering the crop material together at the ends of the channels remote from the mouths by a transverse feed worm to which the stalks are fed perpendicularly. Another alternative is the use of transverse lifting rollers in combination with a worm discharging the crop at a central region to the intake drums of the chopper. These arrangements have also been found to be disadvantageous. Such additional rollers or drums, transverse worms and the like must extend the full width of the chopper, creating additional expenses for supporting and driving these elements and not being fully satisfactory.